Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $84.91   12.626%   $95.6307   $95.63   $95.65   $95.60  
  Purchase #2 $79.55   8.248%   $86.1113   $86.11   $86.10   $86.10  
  Purchase #3 $170.76   10.347%   $188.4285   $188.43   $188.45   $188.40  
  Purchase #4 $81.53   8.720%   $88.6394   $88.64   $88.65   $88.60  
  Purchase #5 $163.31   4.181%   $170.138   $170.14   $170.15   $170.10  
  Purchase #6 $59.36   9.489%   $64.9927   $64.99   $65.00   $65.00  
  Purchase #7 $144.84   12.461%   $162.8885   $162.89   $162.90   $162.90  
  7 purchase totals = $784.26       $856.8291   $856.83   $856.90   $856.70